package cn.xttc.edu.util;

import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.util.Random;

/**
 * 生成验证码的工具类
 *
 * @author yl
 */
public class RandomValidateCode {
    /**
     * 放到session中的key
     */
    public static final String RANDOMCODEKEY = "captcha";
    private final Random random = new Random();

    /**
     * 随机产生的字符串
     */
    private static final String RANDSTRING = "23456789ABCDEFGHJKLMNPQRSTUVWXYZ";

    /**
     * 图片宽
     */
    private static final int WIDTH = 80;

    /**
     * 图片高
     */
    private static final int HEIGHT = 26;

    /**
     * 干扰线数量
     */
    private static final int LINESIZE = 40;

    /**
     * 随机产生字符数量
     */
    private static final int STRINGNUM = 4;

    /**
     * 生成随机图片
     */
    public void getRandomCode(HttpServletRequest request,
                              HttpServletResponse response) {
        HttpSession session = request.getSession();
        //BufferedImage类是具有缓冲区的Image类,Image类是用于描述图像信息的类
        BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_BGR);
        //产生Image对象的Graphics对象,改对象可以在图像上进行各种绘制操作
        Graphics g = image.getGraphics();
        g.fillRect(0, 0, WIDTH, HEIGHT);
        g.setFont(new Font("Times New Roman", Font.ROMAN_BASELINE, 18));
        g.setColor(getRandColor(160, 200));
        //绘制干扰线
        for (int i = 0; i <= LINESIZE; i++) {
            drawLine(g);
        }
        //绘制随机字符
        String randomString = "";
        for (int i = 1; i <= STRINGNUM; i++) {
            randomString = drawString(g, randomString, i);
        }
        session.removeAttribute(RANDOMCODEKEY);
        session.setAttribute(RANDOMCODEKEY, randomString);
        g.dispose();
        try {
            //将内存中的图片通过流动形式输出到客户端
            ImageIO.write(image, "JPEG", response.getOutputStream());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 获得字体
     */
    private Font getFont() {
        return new Font("Fixedsys", Font.CENTER_BASELINE, 18);
    }

    /**
     * 获得颜色
     */
    private Color getRandColor(int fc, int bc) {
        if (fc > 255) {
            fc = 255;
        }
        if (bc > 255) {
            bc = 255;
        }
        int r = fc + random.nextInt(bc - fc - 16);
        int g = fc + random.nextInt(bc - fc - 14);
        int b = fc + random.nextInt(bc - fc - 18);
        return new Color(r, g, b);
    }

    /**
     * 绘制字符串
     */
    private String drawString(Graphics g, String randomString, int i) {
        g.setFont(getFont());
        g.setColor(new Color(random.nextInt(101), random.nextInt(111), random.nextInt(121)));
        String rand = String.valueOf(getRandomString(random.nextInt(RANDSTRING.length())));
        randomString += rand;
        g.translate(random.nextInt(3), random.nextInt(3));
        g.drawString(rand, 13 * i, 16);
        return randomString;
    }

    /**
     * 绘制干扰线
     */
    private void drawLine(Graphics g) {
        int x = random.nextInt(WIDTH);
        int y = random.nextInt(HEIGHT);
        int xl = random.nextInt(13);
        int yl = random.nextInt(15);
        g.drawLine(x, y, x + xl, y + yl);
    }

    /**
     * 获取随机的字符
     */
    public String getRandomString(int num) {
        return String.valueOf(RANDSTRING.charAt(num));
    }
}
